I've posed nude for a photographer in the manner of Rodin's Thinker, but I merely looked constipated.
George Bernard Shaw

The dreamer whose dreams are non-utilitarian has no place in this world. In this world the poet is anathema, the thinker a fool, the artist an escapist, the man of vision a criminal.

Henry Miller

Only he is an emancipated thinker who is not afraid to write foolish things.
Anton Chekhov

The books that help you most are those which make you think that most. The hardest way of learning is that of easy reading; but a great book that comes from a great thinker is a ship of thought, deep freighted with truth and beauty.

Pablo Neruda